Signalling system for radioactive well logging



Feb. 17, 1948. s. KRASNOW ETAL. 2,436,008

SIGNALLING SYSTEM FOR RADIOACTIVE WEL L LOGGING Original Filed Oct. 24,1939 '7 Sheets-Sheet l Fla-2 31 mam/70m;

SHELLEY KEASNOW LEO/VF CORT/L56 36 y iww Feb. 17, 1948. s, KRASNQW ET AL2,436,008

SIGNALLING SYSTEM FOR RADIOACTIVE WELL LOGGING Original Filed Oct. 24,1939 7 Sheets-Sheet 2 /L\ ../57 III. .LLZ O 22 l \A u rzvvz/vro/esJHELLEY k/PAS/Vou LEON f UPTISS 3 b mitfi mur A TTORNEY Feb. 17, 1948.s. KRASNOW ETAL 2,436,008

SIGNALLING SYSTEM FOR RADIOACTIVE WELL LOGGING Original Filed Oct. 24,1939 7 Sheets-Sheet 3 Feb. 17, 1948. s. KRASNOW ErAL.

SIGNALLING SYSTEM FOR RADIOACTIVE WELL LOGGING Original Filed Oct.

24, 1939 '7 Sheets-Sheet 4- lmwsmon; Gaff/as,

-17., 1948. s. KRASNOW ETAL 2,436,00

SIGNALLING SYSTEM FOR vRADIOACTIVE WELL LOGGING Original Filed Oct. 24',1939 7 SheetSSheet 5 Feb. 17, 1948. s, KRASNQW ETAL 2,436,008

SIGNALLING SYSTEM FOR RADIOACTIVE WELL LOGGING Original Filed Oct. 24,1939 7 Sheets-Sheet 7 Patented Feb. 17, 1948 2,4,008 SIGNALLING SYSTEMFOR RADIOACTIVE LOGGING Shelley Krasnow,

Original application 301,078. Divided an 19, 1943, Serial No. 472,894

Arlington, Va Montgomery Count and Leon F.

ombu- 24. mo. Serial No.

e um

application January 18 Claims. (01. 250-83.)

This invention relates to an improved method and apparatus for measuringradioactivity, and has particular reference to a method and apparatusfor measuring radioactivity in inaccessible locations. such as inboreholes or at considerable depths in bodies of water.

One object of the invention is to provide a method and apparatus usefulfor locating deposits of minerals having radioactive properties. Anotherobject of the invention is to provide an apparatus by which one maymeasure radioactive properties continuously from the top to the bottomof a borehole. and have both an immediate indication, and a permanentrecord, of the radioactivity at various depths. I In locating depositsis often the custom to drill a number of boreholes in localities wheresuch deposits might exist. It is further the'practice to bring samplesor cores of the drilled material to the surface of the earth. and thereexamine them for radioactivity by well known methods and apparatus. Thismethod has sible to bring all of tain percentage always being lost inthe drilling or handling.

It is further known that deposits of petroleum are often markedlyradioactive as compared With the surrounding rock material. This isbelieved to be due to the superior absorptive property of petroleum forradium emanation. Natural gas and ground water are also known to besomewhat of radioactive minerals it I more radioactive than theirsurrounding rook material. In drilling for either petroleum or ural gas,or ground water, it is desirable to know the exact level at which thestrata having these are traversed by the drilled hole. This is oftendifllcult to determine, particularly when drilling I has been done bythe "rotary method, in which the use of mud under pressure tends to walloi! the strata. Often too, the drilled hole will be lined with ametallic casing, which casing by accident or intention may seal offstrata having the desired fluid.

It is the intention in the present invention to provide an apparatus sosensitive, and a method appropriate to its use. that the relativelyfaint radioactivity of oil and ground water may be detected in place inplane 8-.

its nature diil'erentiate between the different though'iaintradioactivities of the rock material. Rock materials. dependent upontheir origin and dependent upon the minerals contained in them. havedifferent radioactivities. Thus. it has been taminating them. Organicdeposits.

such as coal, as mentioned above. petrified vegetable matter. etc., willshow higher radioactivities than for instance limestone and chalk. Thus,with an apparatus as sensitive as that described herein it will bepossible to differentiate between different layers of rock by thedifferences in their radioactivities. Each layer in an area will have a.characteristic radioactivity. just as it has a characteristic chemicalcomposition, and for the same reason. Thus. the radioactivity of a layerwill serve as a variety of marker, serving to identify the layerwherever it might be in an area.

It thus becomes possible to identify rock layers in different boreholesdrilled in an area and thus correlate the strata.

Further objects of the invention described are to obviate thedii'llculties mentioned and secure the advantages mentioned above.

Reference is had to the accompanying drawings in which:

Figure 1 represents a simplified form of apparatus for giving 9,continuous photographic record of radioactivity at various depths.

Figure 2 shows a cross section of the members used in Figure 1, takenacross the plane 2-2.

' Figure 3 shows a vertical cross-sectional view of another type ofapparatus adapted to giving a photographic record of radioactivity.

Figure 4 shows a more convenient form of apparatus for measuringradioactivity at various depths in a borehole.

Figure 5 shows a cross-sectional view of the element It shown in Figure4, taken across the Figure 6 shows in the apparatus Figure 7 shows inFigure 6 taken the sensitive element employed shown in Figure 5.

a cross section of the element across the plane 8-6. Figure 8 shows thecircuit diagram of the apparatus shown in Figure 4.

Figure 9 shows a vertical cross-sectional view of still a further typeof apparatus which may be used for the purpose described.

Figure 10 shows the circuit diagram for an improved apparatusconstructed along the lines of thatshown in Figure 9.

Figure 11 shows essentially the same apparatus as is shown in Figure 9with the addition of another electroscope to serve as a control.

Figure 12 shows a means of rendering strata artificially radioactive.

Figure 13 shows a. modification or the apparatus designed to permitperforation of the casing in a well.

Figure 14 shows still another apparatus for measuring and recordingradioactivity at various depths.

Figure 15 shows another type of apparatus for measuring radioactivity atvarious depths and giving an immediate indication at the surface of theground of the value of the radioactive intensity.

Figure 16 shows a detail of the lower portion of the apparatus shown inFigures 14 and 15.

Figure 17 shows a detail of the recording apparatus shown in Figure 14.

Figure 18 shows still another apparatus for measuring radioactivity,which apparatus employs radio transmission conveying information to thesurface of the ground.

Figure 19 shows the electrical circuit suitable for use in themodification shown in Figure 15.

Figure 20 shows a modification of Figure 19 for radio transmission tothe surface of the ground.

Figure 21 shows schematically a system for conveying information to thesurface of the ground by means of mechanical waves.

Figure 22 shows a circuit for causing a change in frequency with changeof radioactive intensity.

Figure 23 shows still another circuit serving the same function as thatshown in Figure 22.

Figure 24 shows still another circuit, utilizing a glow discharge lamp,and serving to vary the generated frequency in relation to the change inradioactive intensity.

Figure 25 shows a modification .of the circuit shown in Figure 24.

Figure 26 shows an apparatus for measuring radioactive gradient.

Figure 27 shows a modification of the apparatus indicated in Figure 26to render measurements of radioactivity more dependable.

Figure 28 shows an apparatus for measuring radioactive intensity withthe interposition of a filter.

Figure 29 shows a side view of the electroscope and ionization chambershown in Figure 10.

' Referring now particularly to Figure 1, I shows a flexible band,preferably metallic, wound upon a reel 2 operated by a crank 3. The bandpasses over a measuring wheel 4 and into the borehole. A photographicfilm is fed from a reel 5a operated by a crank SD. A lobed member 1serves to apply cement to the band I at regular intervals. This cementis fed by a brush 8 from tank 9.

In operation the band I and photographic film film and band together atintervals. The cement used may be of such nature that it will allow theready separation of the two members when they are removed from theborehole. The photographic film reeled out is left in the borehole for aconsiderable period, which may be as much as several days. It is thenwound upon the reel, removed and developed. If a markedly radioactivelayer such as R exists, the film will be found to show a light spot. Bymeasuring the length of film to this spot, the depth of the layer It maybe determined. A film reinforced with strands of fiber or metal may beused and thus the necessity of using the band I obviated. It

5 are reeled together down into the borehole.

is further evident that the film may be coated with any of the standardintensifying materials commonly used in preparing medical X-ray films.The film may also be coated with a substance to render it impervious toany harmful liquids which may exist in the borehole. An opaque coatingmay be applied to the film to allow its use in daylight. If the coatingis properly chosen, it will not materially hinder the passage of raysfrom radioactive material.

In the modification shown in vertical crosssection in Figure 3, acartridge 51 is provided. In this is mounted a clock driven motor 58which serves to wind photographic film 60 upon spool 59, the filmoriginally being on spool SI. Cover 52 is removably fastened tocontainer 57 by means .of any suitable connection, preferably a threadedconnection. A gasket 53 serves to make a fiuid tight seal. The ring 64serves for lowering and raising the apparatus in the borehole. Thecartridge 51 is made of suitably heavy material to prevent collapsethereof under the high fiuid pressure which may exist in a liquid-filledborehole. However, in order to reduce the absorption of radiation by thecartridge a thinned portion 65 is provided. Since this is of small areathe material here may be made quite thin. In operation the clockwork 58would be so set as to maintain the film 60 at a fixed position for apredetermined time. after which it would advance the film so as toexpose a new portion thereof, and would serve to expose this new portionagain for a predetermined period. The operator, knowing the length ofthese periods would maintain the cartridge at a fixed depth for eachsuch period. Because of the slowness with which the film would beaffected, it would not be necessary in most cases to provide any shieldto protect the film from exposure while the apparatus is being raisedand lowered.

A more convenient form of the apparatus shown in Figure 8 employs acartridge II suspended in the borehole by a conducting cable I2. Thecable I2 passes over a measuring wheel l3 and thence onto a reel I4operated by a crank I5. A pair of slip-rings I la and Nb fastened to theshaft of the reel I4 have bearing upon them the brushes I6 and Il. Thesebrushes areconnected through the medium of wires I8, I8, to a recordingelement I9. Referring now to Figures 5 and 6, the cartridge II consistsessentially of a radioactive-sensitive member 23 mounted at the bottomof a pressure-tight cartridge 20. A rack 2| holds the element 23 andserves further to hold batteries 24, vacuum tube 25, and relay 21.Springs 22 serve to prevent violent contact of the frame 2| withcartridge 20. A cap 3| is fastened by means of a threaded or otherconnection 30 onto one end of cartridge 20. A fiuid tight seal is had bythe use of gasket 33. The wires necessary to convey the signals from thecartridge II pass through insulating bushing N and are looped onto ring32 and thence pass to the surface. In this way the wire serves also forraising and'lowering member I I The sensitive element 23 consistsessentially of a sealed glass vessel 35 which has within it a conductingring 38 connected to wire 39 pa ing through seal 40. Through the axis01' ring II another conducting member 30, in a wire or filament. Thismember 38 are kept at a high potential relative to each other by meansof batteries 46 and ll operating through high resistance leak 41, asshown in Figure 8. A suitable value for the voltage of battery 46 is 135volts; or battery 44, 360 volts. The positive end of battery 44 isconnected to one side of the filament 45 of vacuum tube 25. The member38 is connected to a blocking condenser 42 and thence The operation ofthe apparatus is as follows:

members 36 and 38 are charged at a controlled rate to a high potentialrelative to each through slip-ring Mb, brush ll, battery 49,electro-magnet 50, brush l6, and slipring Ma. The energizing of electromagnet 50 will cause armature 5| to move pen 52, causing a break in theline traced on tape 53. It will be noted that upon each closure of thecontacts 28 and 29, the energy conducted downward by the cable iscontrolled by the said contacts to mama 6 or kink in the line traced bythe pen 82. It will be further noted that the operation 01' theappacharacter. peated, with a frequency of repetition proportionate tothe radioactivity sensed by the detecting element. By the operation ofrelay contacts 28 and 28, there is created within the cable a series ofelectric pulses whose frequency characteristics are determined by andrelated to the frequency of operation of the Geiger-Muller tube "-3 Thislatter frequency is in turn determined by the radioactivity, as pointedout herein.

Upon the operation of the circuit in this fashion, the potential ofmember 38 will be restored to its original value, increasing thefilament-toplate current in tube 25, energizing relay 2! and therebycausing the circuit made by members 28 and 29 to open.

Upon the further ionization of the gas in container 35 the operationabove described will be repeated. Thus the frequency of the pulsesfinally received by pen 52 will be a radioactivity of her 68 connectedto an may be of any suitable type, but.which'is shown schematically as agold leaf electroscope employing leaves 1|. Springs 69 serve to cushionof radioactive material is suspected, for a suitnated respectively as 89and 90.

A somewhat more elaborate arrangement than is shown in Figure 9 is thatshown schematically in Figure 10. In this, means are provided to trade14, and thus leaf II.

charge the electroscope periodically on its charge falling off by adefinite amount. The frequency with which the electroscope is charged 18a measure of the ionization current flowing and thus of the intensity ofradiation in the vicinity. Specifically, the apparatus consists of anionization chamber having an outer conducting wall 10 into which isfastened to a stopcock 11 through which a suitable gas, such as air, maybe passed into the chamber. An electrode 14 passes through an insulatorI5 and thence into the electroscope 10. A lamp 81, surrounded by a lighttight housing 86, and having a focusing lens 00, casts a beam of lighton photo-cell 02. This beam will fall on the photo-cell 82 only if theleaf 1| is in the discharged position. In such event a current passesthrough cell 02, relay II, electromagnet 84, and energizing battery 03.The operation of the relay 8i closes contacts 18 and 00, thus causingbattery 18 to recharge the elec- Whenever this event occurs, pen 84a iscaused to move across chronograph tape 85, and thus produce a kink inthe line traced by the pen. The frequency of these kinks is, therefore,a measure of the radioactivity in the vicinity of chamber 16. It willthus be seen that the system composed. of the electroscope, lamp,photocell, etc., in operation gives a repetitive pattern of variation ofelectric current of a characteristic nature and as described, thefrequency of recurrence of the characteristically varying current willbe in proportion to the radioactivity incident upon the ionizationchamber. In this modification, as in the modification shown in Figure,8, the battery 83 at the surface of the earth conducts currentdownwardly through the cable to the apparatus in the borehole. Thiscurrent iscontrolled within the borehole to create electrical pulses inthe cable, which pulses finally appear in graphical form by means of thekinks and marks on the tape 85 by the pen 84a. The system in operationcreates electrical pulses in its normal mode of operation. These pulsesare impressed upon the cable as indicated above. The frequency ofrepetition of the varying electric current of a predeterminedcharacteristic nature is varied in proportion to the radioactivity.

In the types of apparatus shown in Figure 5 and Figure 10, thechronograph and entire recording system may be clock operated andmounted in the cartridge so that no conducting wires, need pass to thesurface. As a further alternative the motion of the tape may be made nota function of time, but rather of the position' of a measuring wheelsuch as I3. In the apparatus shown in. Figure 10, the elements shown as83, 84, 84a, and 85, may be mounted at the surface'of the ground,similar to the mounting of element I9 in Fi ure 4; the rest of theapparatus being mounted in a cartridge suitable for lowering to thedesired location. Thus, all of the elements shown in Figure 10, with theexception of members 83, 04, 04a. and 05, would be enclosed within acartridge and lowered into the borehole. These last named elements wouldbe at the surface of the ground as with similar members shown in Figure4. The battery 83 is thus a source of electrical energy connected to thecable at the surface of the earth. It will be noted that this cable,consisting of two leadsone to photocell, the other to relay coil 8|, isa two conductor type having the source of electrical energy, the battery03, connected to the respective conductors at the surface of the earth.

' ing material I00. In

Another apparatus which may be used for the same purpose is shown inFigure 14. This-consists of a cartridge IOI, which is provided with agas-tight partition I05 and a gas-filled space I02. Located preferablycentrally within the space I02 is an electrode I03, carefully insulatedby means of amber or other low leakage insulatthe partition I05 ismounted a valve IN by which gas may be introduced to attain any desiredpressure within the enclosure I02, after which the valve Ill may be shutand the said pressure maintained. The wall II is made of strongmaterial, as thin as possible to reduce the absorption of rays ofradioactive material passing into the space I02. A material which willcombine strength and transpuency to rays from radioactive substances isutilized. Suitable materials are: Magnesium alloys, aluminum alloys suchas Duralumin, beryllium, or beryllium alloys. A very thin steel housingmay be used, the greater strength allowing the material to be so thinthat absorption is not serious.

' port a steady The space I02 may be filled with any one of a number ofgases. A suitable gas for this purpose is nitrogen, although other gasesmay be used with almost equally good results.

Above the partition I05 is mounted a high voltage battery I00. Connectedto the positive end of battery I06 is a resistor I01, having a highresistance. One terminal of this resistor is connected to the electrodeI03, while the negative end of battery I06 is connected to the conductincasing I0I.

Mounted across the ends of resistance i0! is electroscope I00, having afixed element I09 and a movable element H0. The position of element H0relative to I09 will depend upon the current flowing through resistanceI01, which current will be a measure of the ionization existing betweenelectrode I03 and conducting enclosure IN. The position of element H0 isrecorded photographically by a clockwork driven camera III. The camerais shown more fully in detail in Figure 1'7. 'Here an illuminatingsystem and photographic recording system are all mounted within housingIlla. Battery I20 lights lamp H9, throwing light on transparent plateIII. Plate II8 casts light on elements I09 and H0, allowing the elementsto be photographed through lens'II'I on film 3. A conventional clockworkmotor I I5 drives spool Ill taking film from spool H8, and allowing itto be reeled upon spool III. Figure 16 shows the details of the lowerportion of the apparatus shown in Figure 14, directing particularattention to the insulation employed. It is of advantage to rib orcorrugate the surface of the insulation as shown, to increase theleakage path. Although element IN is shown as a valve, in practice itmay be advantageous to use a standard type of sealed-off glass joint, asemployed in the glass blowing art.

The pressure in the ionization chamber is preferably higher thanatmospheric so as to give a greater ionization current, as will befamiliar to those versed in the art. A pressure of several hundredpounds per square inch will be found suitable. The voltage across thechamber is made as high as possible so as to obtain an increasedionization for a given change in intensity of ionizing rays. The voltageis limited, however, by the fact that if it is made too high, ionizationby collision will result and the chamber will supdischarge regardless ofthe intensity of ionizing rays in its vicinity. The value of theresistance is such as to cause an easily meascording. The centralelectrode I03 of the ionization chamber is connected to element I22which represents schematically the electrical apparatus more fully shownhereinafter. A lead I21 is connected to metallic casing IOI serving toground certain of the elements employed in the appara- If a reel such asI3 is used to lower the apparatus, the depth at any moment can be toldand correlated with the indicated frequency.

Referring now to Figure 19, I and sent the elements of the ionizationThe side I M I03 reprechamber. is grounded, while the electrode I03 Apotentiometer I30 is connected across the terminals of battery I29, withits movable contact I53 connected to the cathode of a triode vacuum tubeI3I. A lead joins electrode I03 and the grid of a pentode vacuum tube I32. While a pentode is shown in the specific embodiment disclosed, anymultielement tube having three or more elements, and having the propercharacteristics, may be used.

A conventional battery I33 is shown to provide the heater current forthe tubes. A "B" battery I34 is shown connected to battery I33 andleading to' choke I35, the other terminal of the choke being connectedto the plate of tube I32. A tap is taken off battery I34 to provide thescreen grid voltage for tube I32. The plate of tube I32 is connectedthrough condenser I36 to inductance I31. Inductance I31 terminates atterminal point I38 to which is connected one end of resistor I39. Theother end of resistor I39 is connected to contact I53 as shown.

Across inductance I31 and resistance I39 is placed a condenser I40. Thecommon terminal point I38 is connected to a grid of vacuum tube I32.While connection to a specific grid has been indicated, it is alsopossible to connect a lead 10 from terminal III to the cathode of tubeI32 or to any other element except the plate of the same tube, withsatisfactory results. It will be understood that proper biasing meanswill be utilized for the specific type of tube chosen.

the contact I53. nected through a conventional self-biasing arrangementI to inductance I31. The plate of tube I3I is connected to the primaryof a coupling transformer I42, the other end of the primary beingconnected to the B battery as shown. The secondary of couplingtransformer I42 may be connected to leads which directly to the surfaceof the bore- A suitable frequency can be chosen, high enough to beeasily measurable, and low enough to avoid difficulties due to capacityand inductance effects along the transmitting cable.

The coupling transformer may be connected to an amplifier such as I54,the amplifier feeding into the external cable as shown. The amplifierwill be found particularly valuable in preventing external loadvariations from reacting on the principal circuit and thus causing adisturbing change of frequency. Alternatively, the amplifier may feeddirectly into an antenna and ground arrangement, or into what isequivalent, a dipole radiating system of a. type common to those versedin the radio art. This modification is shown schematically in Figure 20,I being the antenna or its equivalent and I56 being the ground or itsequivalent. It will be understood that for this modification, a suitableradio frequency will preferably be employed.

As a still further alternative, the amplifier I54 may feed into anelectromagnetic vibrator or sounding device, having an electromagnet I51and an armature or diaphragm I58. The alternating current output of theamplifier I54 will serve to cause an alternating magnetic field ofequivalent frequency in electromagnet I51, which will cause themechanical vibration of armature I58. If this armature is made tovibrate with sufficient amplitude, the mechanical vibrations causedthereby may be made strong enough to allow their transmission to thesurface of the earth where they can be detected by a detector devicesuch as a microphone I59,

amplified by amplifier I00, and their frequency measured by frequencymeasuring device I6I.

It will be understood that the constants in the circuit shown in Figure19 will be chosen in the case aforementioned so as to give a frequencyapproximately within the audio-frequency range. The frequency may bemade quite low, even below the audible frequency. This may be doneeither by selection of the proper constants of the circuit shown inFigure 19, or by the use of a scaling or subharmonic frequency device,incorporated with amplifier I54. The frequency may be made so low that asystem similar to that indicated by the elements 50, 5I, 52, 53, 54, and55, in Figure 8 may be used in place of element IBI.

While Figure 19 discloses an apparatus for generating a frequency inproportion to the intensity of radioactivity, it will be understood thatan apparatus utilizing phase shift or amplitude variation as a functionof radioactive intensity,

may be used instead of one employing frequency variation.

An amplifying stage I62 may be inserted in the lead from element I03 ofthe ionization chamber to the grid of tube I32. This will be a directcurrent amplifier, and will serve toincrease the voltage change on thegrid for a given change in potential on element I03. Where the change inpotential on element I03 is sufficient to cause a proper voltage changeof the grid, the amplifier I62 may be omitted, and a direct connectionmade between the lead I03 and the grid element.

The operation of the circuit as follows:

The elements I31, I39, and Ill, together with tube I3I, biasingarrangement III, and the proper A and B voltage supplies, constitute anoscillatory circuit whose natural frequency is dependent on the valuesof inductance I31, condenser I40. and resistance I39.

There will be an alternating voltage across the terminals of resistanceI39, which voltage will be in phase with the current flowing through theresistor. This voltage will be impressed between the cathode and onegrid of tube I32, and will cause in general an alternating voltage ofthe same frequency between the grid and plate of tube I32. The-voltageacross resistor I39 is 90 out of phase with that across I31.Consequently, the voltage impressed by vacuum tube I32 across inductanceI31 will also be 90 out of phase with the voltage in inductance I31. Themagnitude of this voltage will be dependent upon the amplification dueto tube I32. Any out-ofhase voltage across inductance I31 will have theeifcct .of changing the apparent value of the inductance and willthereby cause a change in the frequency generated by the oscillatorycircuit;

Any increase in radioactive intensity will alter the effectiveresistance between the electrodes IN and I03. Through the agency ofbattery I29, an increased current will flow through the circuit composedof battery I29, resistance I23, and electrodes IIII and I03. Thisincreased current will cause a greater voltage drop between terminals ofresistance I26, which increased voltage drop, after amplification byamplifier I62, will be impressed across the cathode and a grid of tubeI32. .If the screen grid voltage has been properly adjusted, any changein the potential of the grid connected to amplifier I62, will cause achange in the efiective ampliflcation factor of tube I32. This change,as described previously will cause a change in-the out-of-phase voltageimpressed across inductance I31 and will thereby cause a change in thenatural frequency of the oscillatory circuit described herein. Thealternating current flowing through inductance I31 will induce voltagesof equal frequency in transformer I42 and consequently in amplifier I64.

It is therefore seen that an alteration of radioactive intensity willcause a related and functionally connected change in frequency in theoutput of amplifier I63.

As in the modification shown in Figure 14, the voltage of battery I29should be so chosen'as to obtain the maximum ionizingefiect withoutactual breakdown, and the value of resistance I26 should be of suchvalue as to cause a significant voltage change across the cathode andgrid of tube I32. The values of the constants in the remainder of thecircuit should be chosen so that with the may be described for elementsI3I and I32, a suitable set will be had by using an RCA type #957 tubeas element I3I and an RCA type #959 tube as element I32. 1Suitablevalues for the other elements are as folows:

129 volts 134 135 volts 128 lihmegohms 170 1800 ohms and .01 m1. 136.002 mf.

137 '100 microhenrys 140 20 mmf.

141 50,000 ohms and .0005 mf, 139-"; 100 ohms As described herein, thefrequency may vary over a wide range, depending upon the particular modeof transmission of information to the surface. A suitable frequency isone megacycle.

Figure 22 shows still another modification making use of alternatingcurrents only across the electrodes IIII and I03 of the ionizationchamber. I43 represents the inductance of the plate reso-' nant circuitof a standard vacuum tube oscillator. The mode of construction of suchan oscillator will be well understood by those versed in the art and nofurther explanation thereof need be given here. Inductance I44constitutes an element which is inductively coupled to element I43. Oneterminal of inductance I44 is connected to electrode I03, while theother terminal is connected to the terminal IIII of the ionizationchamber. The elements of the circuit should be so proportioned that themaximum voltage developed across elements IN and I03 will be of theproper value for the particular mode of construction and particularpressure utilized in the ionization chamber. The circuit constants arefurther chosen so as to give the desired frequency, which may be anyusual audio or radio frequency. Any change in the conductivity of thegas between elements IOI and I03 will cause an altered current to flowin inductance I44. This will have the effect of altering the naturalfrequencyof the system composed of the plate resonant circuit and theinductively coupled element I44. This frequency may be transmitted toany other inductively coupled element I45, which element will serve thefunction of the secondary of transformer I42.

Suitable values employed in the above modification are a voltage ofbetween 100 and volts across the elements of the ionization chamber, anda natural frequency in the vicinity of two megacycles in the oscillatorycircuit.

Another system which may be employed is shown in Figure 23. Here elementI43 is an inductive element in the plate resonant circuit of aconventional vacuum tube oscillator. Across the terminals of thisinductance are connected condenser I46 and resistance I41 in series.Across the terminals of condenser I46 are connected the elements I03 andIIII. Any change in the current flowing between electrodes IIII and I03will cause an alteration in the effective natural frequency of thesystem composed of the elements shown. This change may be detected in anadditional inductively coupled element I45, which again may be connectedin place of the secondary of transformer I42.

Still another modification may be utilized for .the photographicobtaining a frequency change in radio activity in the vicinity ofelements II minal of the primary II is connected to a glow dischargelamp I50, the other terminal of the discharge lamp being connected toelement III I.

In operation a current will flow between electrodes lIiI and I03depending upon the ionizing A further modification making use of a glowdischarge lamp is shown in Figure 25. Here element I03 is connected tothe positive end of a condenser I49.

The operation of this circuit is analogous to that of the modificationshown in Figure 24, the difi'erence in impedance of the ionizationchamber causing a different frequency of discharge of the glow dischargelamp. The pulses thus generated are transmitted to the secondary In asbefore.

It will be understood that if a glow lamp is used as the dischargedevice itwill flicker at a rate dependent upon the radioactive intensityin the vicinity of the ionization chamber. The rate of flicker may beobserved visually if the glow lamp is at an accessible locality. Therate of flicker may also be observed indirectly by photographic means.Thus the glow lamp may be substituted for the apparatus shown as III) inFigure 17, and may be allowed to record on the photographic film H3. Aseries of streaks will be obtained on film, the number of streaks perunitlength of film being directly related to the radio-active intensity.The glow lamp may further be allowed to act upon a photocell, therebygenerating a frequency in the photocell circuit directly related to thefrequency of the flashes. Where the photocell has an integrating actionwith respect to time, the intensity of current flowing in the photocellwill be directly related to the frequency of discharge of the glow lamp.

It is further to be noted that a glow lamp may be substituted forelement I42 in the circuit emanother element having sistancecharacteristics.

Figure 26 shows an apparatus which may be utilized to measure what maybe termed as the may be detected.

This modification will permit further distinguishing the actualradioactivities of the strata from the possible individual erraticbehavior of each of the measuring elements,

If the latter feature is sought rather than the acne] measurement ofgradient of radioactivity, the measuring elements may be placed closetoscribed. Difi'erent materials may be introduced in the borehole, eachhaving different radioactive properties. They may later be identified bymeasurements taken with a filter.

The apparatus shown in Figure 28 resembles that shown in Figure 14,except that an outer cylindrical shield or filter I 64 has been placedcompletely surrounding the cartridge IOI. A latch I65 is held by aspring in an indentation I66 in the filter. This latch may be operatedby a solenoid IB'I actuated by wires I68 which pass to the surface ofthe borehole, On passing an energizing current through wires I68,solenoid Iil will cause latch IE! to be withdrawn from indentation I,allowing filter ill to drop till it strikes the circumferential stop m.

With filter I61 in the raised position, the apparatus will operate aspreviously described. The only filtering action will be that of thecartridge, and which is intrinsic in the material used. If it is desiredto take the measurement with'a filter,

the energizing current can be applied while the apparatus is in theborehole, which will cause the filter to assume an operative position,after which a further measurement can be taken. filter I64 against stopionization chamber radially will have to pass through the filter. Sincemost of the rays enter the chamber in this way, the equivalent of anearly complete filter will be obtained.

The filter may be made of any metal or substance having the desiredabsorbing. properties. Examples of suitable materials are copper, lead,aluminum, etc. It is understood that the filter may be incorporated withthe cartridge llil, and be made permanent, in which case only thefiltered rays will impinge on the instrument.

There will be a special advantage in the utilization of the filter aboutone of the units shown in Figure 26 or 2'7. Here a differential resultwill be obtained, giving to the observer the difierence between thefiltered and unfiltered rays. Alternatively, filters may be used aboutboth of the Figures 26 and 2'7, a difierent filter being used about eachelement. By successive runs, with different pairs of filters, the datacollected will be of greater value than that obtained by the meremeasurement of unfiltered radiation.

The apparatus shown in Figure 5 particularly, may be made extremelysensitive to the rays emitted by radioactive substances and so thesometimes faint radioactivity of petroleum, natural gas and ground waterdetected. As has been pointed out previously, this may be done in spiteof any covering of mud or of metallic casing intervening between thewalls of the borehole and the cartridge II. It is in fact, possible torun the cartridge ll inside of the standard drill pipe used in rotarydrilling and thus make measurements with a minimum of disturbance todrilling. Because of the limited absorptive power of the metalscustomarily used for drilling, it will be possible to detect radioactiverays through the thickness of metal in the drill pipe, or even throughthe several inch thickness of the drilling tools.

while, from what has been disclosed above, it is evident that strata maybe diilerentiated from each other by means of the quantitativedlflerence in the amount of associated radioactive material, it will beappreciated that strata need not necessarily be widely diflerent intheir associated radioactivity to enable one to diflerentiate them fromone another. In cases where the associated radioactivities are notconspicuously different in conducting measurements from one end of theborehole to the other, valuable information may still be obtained byconsidering the manner in which the radioactivity varies, or phraseddifferently, the function by which radioactive intensity changes as thedepth is altered. This will be found particularly valuable in searchingfor oil deposits. It will be recalled that petroleum deposits in thenatural state have water associated with them. In many cases the waterunderlies the petroleum, and will have a elements shown in radioactivitymarkedly different from that of the petroleum itself. us if an apparatusas delis all rays entering the scribed above, were lowered past aformation, a sudden change would be observed in passing from rock topetroleum, another sudden change in passing from petroleum to -water,and still another sudden change in passing from water to rock. Thelayers might thus be easily identifiable despite the fact that theirradioactivity may be no greater or less than that of most or the rocklining the borehole.

In certain localities, petroleum in particular may be found to have alimited radioactivity; so limited that detecting its presence with theapparatus shown becomes difficult. In these cases advantage may be takenof the superior absorptive power of petroleum for radium emanation gas.Radium emanation gas may be introduced at the surface of the borehole,being pumped intoit so as to reach the lowest level. The borehole maythen be cleaned .out with a suitable fluid, such as water, and a testmade for radioactivity in the manner described previously. It will beseen that if any petroleum exists in the borehole, it will absorb radiumemanation gas in greater proportion than the other strata, and willtherefore exhibit a stronger radioactivity.

Figure 12 shows an arrangement for performing the above operation. Herea gas container is shown schematically as 9|. This contains the radiumemanation gas (sometimes known as radon"). A pump shown schematically as92 serves to draw the gas from the tank 9! and pump it down throughconduit 93. The gas emerges at the opening 94 of the conduit 93. A layerhaving superior absorptive properties for radon gas, such as an oilbearing layer, will absorb the gas more rapidly than the other layers.Such an absorbing layer is shown as-R. In this instance the borehole isshown as being full of fluid through which the gas is bubbled.

While radon gas has been mentioned as a suit able material, it will beappreciated that other substances having radioactive properties may bement. Heretoiore,

used instead. Such other substances may be radioactive salts, eitherthose having a natural radioactivity or those having an artificiallyexcited radioactivity. It is only necessary for the purpose of theinvention that the substance used be selectively absorbed by the layerof interest within the borehole.

It will further be appreciated that in some cases the lack or absorptionof the radioactive materials by a layer will serve to identify thelayer. In still other cases, the absorption, due to a layer,

may be so great, that the area in the region of the layer will bedenuded of radioactive material, and will appear less radioactive thanthe area in which the absorption is less. In all cases, however, thedifierences between layers will be identifiable by the diflerences inresidual radioactivity,

It is obvious that any other means than those shown or describedmay beused to convey the frequency of the impulses produced by the apparatusin Figure 5 or in Figure 10, to the surface.

The elements employed in the member ll may be combined with aperforating tool as ordinarily used for perforating casing in-oil, gasor water wells. With this it will be possible to lower the apparatusslowly until an indication of radioactivity is received. The apparatusmay then be stopped and the perforating procedure carried on as usual.This will have the advantage of eliminating the inaccuracy usually madein measureit has been the custom to measure the depth to the level inquestion, then 17 run the pcrforator to that depth. This involved twomeasurements, the combined error of which was at times suillcient tocause perforation to be wrong level. 'lhe method dement of depth.

A schematic showing of this appears in Figure 13. Here an apparatuscapable of measuring radioactivity is shown schematically as 91. This isconnected to a perforating element 99. This latter arrangement may be ofany of the well known types. However, the type known as a "gunperforator, which perforates the casing by firing bullets through thecasing, will be found particularly suitable. The assemblage made up Ofradioactive apparatus 91, connector 98 and perforating element 99 may beraised and lowcred by means of cable i". This cable will serve both forraising and lowering an for operating the apparatus and makingobservations. The cable passes over wheel it, onto reel 80. Conmotion ismade between the reel and apparatus ll. Apparatus II serves to makeobservations and to control the elements that are being raised andlowered.

In cases in which the apparatus shown in Figure 18 is used. it will beunderstood that measurements in a dry borehole will ordinarily becontemplated. In order to make this technique most effective, it will bepreferable to employ a radio wave of wave length comparable with thediameter of the borehole. With such a wave length, the borehole will actas a type of tube guiding the radio waves to the top of the hole. Such amodii'ication will operate even though the borehole be filled. orpartially filled. with liquid.

In application Serial No. 137.380, filed April 16, 1937, entitled Methodand apparatus for measuring radioactivity, there i particularlydescribed and claimed methods and apparatus for quantitatively measuringradioactive properties of formations encountered at dillerent depthsinside of drill holes and determining the variation of the saidproperties with the depth of the drill hole. In application Serial No301,078, filed October 24. 1939. entitled Method and apparatus formeasuring radioactivity, there is particularly described and claimedapparatus and methods for measuring radioactivity in deep narrowboreholes including an oscillatory circuit to generate oscillations. theoscillations generated being dependent upon the intensity ofradioactivity and measurement of frequencies generated as a measure ofradioactive properties in the borehole. The instant application is adivision of said application Serial No. 301.078. In application SerialNo. 415,826, filed October 20, 1941, entitled Radioactive well loggingmethod and apparatus, now Patent No. 2,384,840, there is particularlydescribed and claimed apparatus and methods in which a detector such asan ionization chamber generates a current whose value is dependent uponthe intensity of radioactivity in a drill hole and the generation of aseries of impulses thereby, the impulses being determined in accordancewith the radioactivity together with transmission of the impulses andtheir determination at the surface. In application Serial No. 422,450,filed December 10, 1941, entitled Method and apparatus for directrecording of borehole radioactivity, now Patent No. 2.409.436, there isparticularly described and claimed apparatus and method for measuringradioactivity in which the radioactive rays impinging on the detectorelement are modified by a filter. also continuous members sensitive toradioactivity are utilised in detecting the radioactivity. Inapplication Serial No. 433.212, filed March 8, 1942, entitled Radiantenergy activation, there is particularly described and claimed theintroduction of radioactive material into a borehole to be selectivelyabsorbed therein and determination of the radioactivity after suchintroduction. In application Serial No. 452,228, filed July 24, 1942.entitled Multiple element radioactive ray recording, there iparticularly described and claimed the measurement of radioactivityparticularly in geological formations in which several measurements aremade. one with the interposition of a filter element and the otherwithout or where two sets of measurements are made under dln'erentconditions insofar as ray penetration is concerned.

The scope of the invention is defined by the appended claims:

1. In an apparatus for the measurement of radioactivity in a deep narrowborehole, a holder of narrow lateral dimensions capable of fitting intothe borehole and capable of being lowered to various depths therein, thesaid holder including a detector sensitive to rays from radioactivesubstances to produce responses thereto. and amplifying means to amplifysaid responses. a cable leading from the holder to the surface of theearth. a source of electrical energy connected to the said cable at thesurface of the earth to provide the energy for transmitting signals upthe cable. means carried by the said holder operated by the saidamplifying means and controlling the energy conducted from the surfaceof the earth in such manner as to create within the cable a' pulsatingsignal having a property determined by the said rays, and means at thesurface of the earth for receiving and recording the pulsating signaltransmitted by the said cable.

2. In an apparatus for the measurement of radioactivity in a deep narrowborehole. a holder containing a detector sensitive to radioactive rays.means to charge the elements of the said detector to a high potentialrelative to each other so as to obtain a response indicative of theradioactivity within the borehole. means associated with the saiddetector to supply a signal whose properties are indicative of thetransfer detector, a cable connected means to transmit the said signalto the surface of the earth. a source of electrical energy connected tothe said cable at the surface of the earth the electrical energy fromthe said source being controlled by the signal supplying means to createthe signal within the said cable.

3. In an apparatus for the measurement of radioactivity in a deep narrowborehole. a holder of narrow lateral dimensions capable of fitting intothe borehole and capable of being lowered to various depths therein, thesaid holder including a Geiger-Muller detector sensitive to rays fromradioactive substances to produce responses thereto, amplifying means toamplify said responses. a. cable leading from the holder to the surfaceof the earth, a source of electrical energy connected to the said cableat the surface of the earth to provide the energy for transmittingsignals up the cable, means carried by the said holder to create apulsating signal in the said cable dependent on said responses and meansat the surface of the earth for receiving and recording the pulsatingsignal transmitted by the said cable.

4. In an apparatus for the measurement of l9 rays from radioactivesubstances, means to create a varying electric current having apredetermined repetitive nature, including means sensitive to theradiations from radioactive substances, the sensitive meansbeing adaptedto correlate a characteristic of the said varying current with theintensity of radioactivity, means to transmit the said varying currentto a distant point, and means to receive and record the said varyingcurrent at a distant point so that the radioactive strength in thevicinity of the sensitive member may be determined at the distant point.

5. In an apparatus for the measurement of radioactivity within a deepnarrow borehole, a narrow holder capable of being lowered within theborehole and containing a detector sensitive to radioactivity andauxiliary apparatus to amplify the responses of said detector, a cableserving to raise and lower the said holder and to provide electricalcommunication between the said holder and apparatus at the surface ofthe earth, means at the surface of the earth to supply direct currentenergy through the intermediacy of the cable to the holder to providethe energy for transmitting signals up the cable, means within theholder operated by the said auxiliary apparatus to control the energyconducted to the holder by the said cable in intermittent manner tocreate pulses indicative of radioactivity for transmission up the saidcable to the surface of the earth and means at the surface of the earthfor receiving and recording the pulses indicative of radioactivity.

6. In an apparatus for the measurement of radioactivity in a deep narrowborehole, a holder of narrow lateral dimensions capable of fitting intothe borehole and capable of being lowered to various depths therein, thesaid holder including a detector sensitive to rays from radioactivesubstances to produce responses thereto and amplifying means to amplifysaid responses, a cable leading from the holder to the surface of theearth, signalling means to transmit a pulsating signal dependent uponthe amplified responses up the cable, a direct current source ofelectrical energy connected to the said cable at the surface of theearth to provide the energy for transmitting signals up the cable, andmeans at the surface of the earth for receiving and recording thepulsating signal.

'7. In an apparatus for the measurement of radioactivity in a deepnarrow borehole, a holder containing a detector sensitive to radioactiverays, means to charge the elements of the detector to a high potentialrelative to each other so as to obtain a response indicative of theradioactivity within the borehole, means associated with the saiddetector to supply a signal whose properties are indicative of thetransfer of charge within the detector, a cable connected to the lastnamed means to transmit the said signal to the surface of the earth, adirect current source of energy connected to said cable at the surfaceof the earth the electrical energy thereby conducted by the cable to theholder being controlled by the signal supplying means to establish thesaid signal in the cable.

8. In an apparatus for the measurement of radioactivity, means to createa varying electric current having a characteristic predeterminedrepetitive nature, including an ionization chamber having electrodesexposed to radioactive rays, a direct current source of electricalenergy connected to the said chamber to charge the electrodes thereof,the frequency of repetition being flow in said chamber being dependentupon the radioactivity proximate thereto, means to create an electricalsignal mounted upon the holder including the said ionization chamber andadapted to generate electrical pulses whose characteristics aredetermined by and related to the transfer ofcharge in the ionizationchamber, means to transmit the pulses to the surface of the earth, meansat the surface of the earth to receive and record the pulses so as toiumish at the surface of the earth a record of the radioactivity atvarious depths within the borehole.

10. In an apparatus for the measurement of radioactivity within a deepnarrow borehole, a holder having narrow lateral dimensions'capable offitting within the borehole and being lowered to various depths therein,an ionization chamber having electrodes mounted upon the said holder,means to impress a direct current voltage across the electrodes of theionization chamber so that the current flow therethrough will beproportional to the radioactive intensity in the vicinity of theionization chamber, means including the said ionization chamber mountedupon the holder to generate electrical pulses having a characteristicdetermined by and related to the transfer of charge between theelectrodes of the said ionization chamber, means to transmit the pulsesto the surface of the earth, and means to receive and record the pulsesat the surface of the earth thereby furnishing at the surface of theearth a record of radioactivity at different depths within the borehole.

11. In an apparatus for the measurement of radioactivity in a deepnarrow borehole. a holder of narrow lateral dimensions capable offitting into the borehole and capable of being lowered to various depthstherein, the said holder including a detector sensitive to rays fromradioactive substances to produce responses thereto and amplifying meansto amplify said responses, a two-conductor type cable leading from theholder to the surface of the earth, a source of electrical energyconnected to the said cable at the surface of the earth electricalenergy being conducted downward into said holder by the cable, meanscarried by the said holder to control the said electrical energyconducted thereto to form a pulsating signal within the said cabledependent on said responses, and means at the surface of the earth forreceiving and recording the pulsating signal transmitted by the saidcable.

12. In an apparatus for the measurement of radioactivity in a deepnarrow borehole, a holder of narrow lateral dimensions capable offitting fying means and to the said cable to control ourrent conductedto said controlling means by the said cable in accordance with theamplified responses. the terminals of the cable at the surface of theearth being connected to slip rings, brushes bearing respectively onsaid slip rings, the said brushes being connected in series with abattery and a recorder, whereby the recorder is actuated by virtue ofthe connection to the battery, the said cable, and the said controllingmeans.

13. In an apparatus for the measurement of radioactivity, a systemcomprising an ionization chamber having substantially spherical innerand outer electrodes, having associated therewith an electroscope, abattery to charge the elements of the chamber. a lamp and photocellbeing arranged on either side oi the said electroscope whereby the saidelectroscope will allow the beam from the lamp to pass or to be obscureddepending on the state 01' the charge thereoi, a relay connected to thesaid photocell to eil'ect the charging of the ionization chamberelements periodically on its charge falling oil by a definite amount,the e1ectrodes of the said ionization chamber being exposed toradioactive rays, whereby a pulsating current whose frequency is ameasure or the radioactivity in the vicinity of the said ionizationchamber is produced.

14. The combination with an instrument adapted to be lowered by aconducting cable into a well here for indicating conditions therein atdifferent levels, the said instrument having an element thereinproducing an optically observable indication oi the quantity to bemeasured, or means for correlating the record or said instrument interms oi well depth, comprising: an

actuator incorporated in said instrument for causing a predeterminedcycle of operation of said instrument after initiation of operationthereof; and apparatus at the well surface and electrically associatedwith said instrument through said conductor cable, including means forindicating initiation of a cycle oi operation, means for controllingsaid actuator to cause repetition oi said cycle 0! operation, and meansfor indicating the position oi said instrument in the well bore.

15. The combination with an t adapted to be lowered by a conductor cableinto a well bore for recording conditions therein at different levels,01' means for correlating the record or said instrument in terms of welldepth, comprising: an actuator incorporated in said instrument forcausing a predetermined cycle 0! operation of said instrument afterinitiation of operation thereof; a recording device at the surface ofthe well bore for indicating movement of said cable; and meansoperatively connected with said instrument and recording device forindicating on said recording device initiation of each cycle ofoperation.

16. An apparatus for exploring variations in sub-atomic bombardment in aformation confronting a well bore comprising: a housing; a cable forlowering said housing into a well bore; a detector 01 sub-atomicbombardment within said housing; a recorder for said detector alsocontained within said housing and including a record strip adapted toadvance as said recorder is operated means operated by the said detectorto mark a record upon the record strip indicative of the sub-atomicbombardment sensed by the said detector, and means associated with thesaid recorder to move the record strip at a known and controlled rate,means to indicate the depth to which the apparatus has been lowered,whereby the record strip may be interpreted in terms of well depth.

SHELLEY KRABNOW. LEON I. OUR'IISB.

REFERENCES CITED The following references are of moord in the tile ofthis patent:

UNITED STATES PATENTS

